In which type of bond are electrons shared equally?

Electrons are shared equally in a non-polar covalent bond due to the symmetry in electronegativity between the atoms involved in the bond. In non-polar covalent bonds, the two atoms have similar or identical electronegativities, which means they have the same tendency to attract electrons. This results in a balanced sharing of the bonding electrons, leading to no significant difference in charge distribution across the molecule.

In contrast, polar covalent bonds occur when there is a difference in electronegativity between the two atoms, causing one atom to attract the shared electrons more than the other, resulting in a partial charge. Ionic bonds involve the transfer of electrons from one atom to another, creating charged ions, while metallic bonds involve a 'sea of electrons' that are not shared between specific atoms but are delocalized across many atoms in the metallic structure. Thus, this highlights the unique nature of non-polar covalent bonds in terms of equal electron sharing.